{"product_id":"takahashi-collimating-eyepiece-newtonians-cassegrains","title":"Takahashi Collimating Eyepiece for Newtonians \u0026 Cassegrains","description":"\u003ch3\u003e\u003cstrong\u003eProduct Overview\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe Takahashi Collimating Eyepiece is a machined aluminum sighting tool that inserts into a standard 1.25″ (31.75 mm) eyepiece holder or focuser drawtube. Looking through the central peephole, you see the reflection of your primary mirror (on a Newtonian) or secondary\/corrector assembly (on a Cassegrain or Ritchey-Chrétien) centered on the sighting hole when the optics are aligned. It has no lens elements — this is a mechanical collimation tool, not a viewing eyepiece. At 35 mm in diameter, 45 mm long and 45 g, it threads onto the \u003ca href=\"\/products\/takahashi-newtonian-collimating-tube-crosshair\"\u003eNewtonian Collimating Tube with Crosshair\u003c\/a\u003e for a combined Cheshire-eyepiece setup, or works on its own for a quick sighting check.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eWho It's For\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThis is a good match if you own a Newtonian reflector and adjust your own mirror collimation, or if you run a Cassegrain or Ritchey-Chrétien telescope and check secondary mirror alignment between imaging sessions.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eKey Features \u0026amp; Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMachined aluminum body:\u003c\/strong\u003e holds a consistent, repeatable fit in the focuser or eyepiece holder.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFixed 1.25″ barrel:\u003c\/strong\u003e drops straight into any standard visual back or drawtube, no adapter needed.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReflective sighting face:\u003c\/strong\u003e shows the primary mirror or secondary assembly reflected back through the peephole, centered when collimation is correct.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompact and pocketable:\u003c\/strong\u003e 35 mm diameter, 45 mm long, 45 g — easy to keep with your other collimation tools.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003e\u003cstrong\u003eOptical \/ Mechanical Design\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eThe tool is a simple sighting tube: a small peephole at the eye end and a reflective surface at the objective end, with an M36.4 x 1 male thread on the objective side. Used alone, it gives you a fast go\/no-go check of primary mirror centering on a Newtonian. Threaded onto the \u003ca href=\"\/products\/takahashi-newtonian-collimating-tube-crosshair\"\u003eNewtonian Collimating Tube with Crosshair\u003c\/a\u003e, the two work together as a Cheshire eyepiece — the tube supplies a wire crosshair reference, and this eyepiece supplies the sighting hole, giving you a repeatable reference point for centering the secondary mirror shadow on Takahashi Epsilon astrographs and other Newtonian designs.\u003c\/p\u003e\u003cp\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/TKA00441-schema.png?v=1786912645\" alt=\"Takahashi collimating eyepiece TKA00441 half-section dimensional schematic\" style=\"max-width:100%;height:auto;\"\u003e\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eRecommended Uses\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003ePre-session collimation checks on Newtonian reflectors; secondary mirror centering on Cassegrain and Ritchey-Chrétien telescopes; a first-pass sighting reference before fine-tuning with a laser collimator or star test.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eCompatibility and Accessory Notes\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eFits any 1.25″ (31.75 mm) focuser drawtube or eyepiece holder. The M36.4 x 1 male thread on the objective end mates with the Newtonian Collimating Tube with Crosshair for combined Cheshire-eyepiece alignment on Newtonian and astrograph optical tubes.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eGood to Know Before You Order\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eIt has no lens elements.\u003c\/strong\u003e It is built for sighting down the optical axis, not for viewing the night sky — a standard eyepiece handles that job.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIt does not include a crosshair.\u003c\/strong\u003e The crosshair reference for secondary mirror centering comes from the paired Newtonian Collimating Tube, which threads on separately.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eIs it difficult to set up?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eNo. It inserts into the focuser exactly like an eyepiece, with nothing to calibrate before use.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is it best used for?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eChecking whether a Newtonian primary mirror or a Cassegrain\/RC secondary is centered on the optical axis.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDoes it work for astrophotography setups?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt is a visual alignment tool used before imaging, not a component of the imaging train itself.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eDo I need the collimating tube as well?\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eFor a full Cheshire-eyepiece setup with a crosshair reference on a Newtonian, yes — the two are designed to thread together.\u003c\/p\u003e\u003ch3\u003e\u003cstrong\u003eBottom Line\u003c\/strong\u003e\u003c\/h3\u003e\u003cp\u003eA machined 1.25″ sighting tool for checking mirror alignment on Newtonian, Cassegrain and Ritchey-Chrétien telescopes, usable alone for a quick check or threaded to the collimating tube for a full Cheshire-eyepiece reference.\u003c\/p\u003e","brand":"Takahashi","offers":[{"title":"Default Title","offer_id":54047077204079,"sku":"TAK-TKA00441","price":72.93,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0686\/0049\/6239\/files\/tce0020_2_2.jpg?v=1786912905","url":"https:\/\/ontariotelescope.com\/products\/takahashi-collimating-eyepiece-newtonians-cassegrains","provider":"Ontario Telescope and Accessories","version":"1.0","type":"link"}